Benjamin Brink/The OregonianSkye Leslie regularly works out at the Mt. Park Recreation Center. Exercise saved her life, she says.

At her heaviest, Skye Leslie hated to move. Her feet hurt. Her back ached. She wore a cast on one leg because her knee wouldn't support her weight.

To comfort herself, she ate, the more sugar the better. Chocolate was her nightly companion. After work, she'd sit on the couch and consume 3 pounds of Hershey bars with almonds, followed by half a gallon of ice cream.

Over 20 years, Leslie, 62, who was "always thin" and a runner in high school, watched her weight grow from 125 pounds to 339.

"It becomes isolating," she says. "I ate at night, alone."

Sick and tired all the time, she joined a health study at Oregon Health & Science University and learned she was morbidly obese. A mother of three grown children, with an administrative job at OHSU, she also learned she could die 20 years early. The final straw came one morning, five years ago, when she woke up with a temperature of 105. During her two weeks in the hospital, doctors told her she had diabetes. She faced a choice: Change or die.

Evolution of a couch potato

Bruce Springsteen was wrong. We were born to walk, not run. We were also born to climb, forage and migrate.

About 3.5 million years ago, we stood on two legs so we could better peer over savanna grasses and look for dinner. Anthropologists have established that walking was the most efficient stride for distance travel. Compared with four-legged creatures, we're not so great at running. But we can outwalk them and stalk antelope until they keel over from exhaustion.

The problem is, we're lazy. Since our Paleolithic ancestors roamed the plains 80,000 years ago, we've become awfully good at finding ways to expend less energy doing stuff. We used to be a people in motion -- hunting, gathering and finding shelter efficiently. But about 12,000 years ago, we quit running after animals and started herding them. We discovered agriculture and began planting and storing food. That led to staying put in towns and cities, but the term "couch potato" would not be coined until the 1970s.

Chairs, which had been around since the ancient Egyptians, went from items of privilege to widespread use during the Renaissance. There's also a theory that humans became sedentary when Europeans began wearing shoes during the Renaissance. Apparently, their shoes were killing them, so they didn't stand around for long.

But everyone agrees the Industrial Revolution (1750-1850) finally allowed everybody to sit down, which we've been doing ever since. Before that, human muscles provided a third of the energy used in American agriculture and manufacturing. Now, thanks to John Deere, Henry Ford and the assembly line, that percentage is tiny.

Until the 1960s, a majority of jobs involved moderate physical activity. Now, 80 percent are almost completely sedentary. But, our bodies aren't designed to sit eight hours a day. As technology improved -- from steam engines to Twitter-- we've become sitting ducks for disease. And it could get worse. Someday, robots will do everything for us, and we'll even stop picking up the TV remote.

"We've taken physical activity out of the workday," says Dr. Kerry Kuehl, an expert in sports medicine at Oregon Health & Science University. "We used to burn 400 calories a day (working). Now, it's zero."

-- David Stabler

"I chose to live," she says.

Exercise saved her, she believes.

You've heard this news: We have become a sedentary nation, and it's killing us.

– Sitting more than three hours a day can shorten your life by two years, even if you're otherwise active.

– Americans sit an average of 7.7 hours a day.

– Watching TV more than two hours a day can cut 1.4 years off your life. We average four hours of TV a day.

– North Americans lead the world in not exercising. Numbers vary, from 48 to 66 percent of Americans not meeting the minimum requirement of 20 minutes of moderate exercise a day.

– Inactivity accounts for 18 percent of preventable deaths, almost the same rate as smoking.

– In the 1960s, close to half of all jobs required physical activity. Today, less than 20 percent do.

In short, your chair can be deadly.

Exercise: the new medicine

Lack of exercise is such a problem, doctors are beginning to treat it as a medical condition. Since December, medical experts at Kaiser Permanente in Portland and other Northwest cities routinely ask outpatients about exercise. It's become so important, doctors now consider exercise a vital sign, along with weight, blood pressure, temperature and pulse.

Risk factors include recliners, big-screen TVs, long commutes and sitting all day, he says.

In the nine months so far, 41 percent of Kaiser outpatients said they were inactive, Bachman says, which is line with national figures. Another 37 percent said they met the recommended weekly goal of 150 minutes of activity. The remaining 22 percent reported getting 31 to 150 minutes of exercise weekly.

Data also show that people who live in the suburbs are less active than urban dwellers, Bachman says.

"More people are driving, and they're biking less in the suburbs," Bachman says.

Sitting for long bouts is so bad that the effects can't be erased even if you exercise at other times of the day. An Australian study found that people who sat for more than four hours a day were twice as likely to be hospitalized or die from a major cardiac event compared with those who sat for two hours or less. The numbers held true no matter how much exercise the subjects got. That suggests muscles that don't contract for hours undergo harmful metabolic changes.

Olivia Bucks/The Oregonian/2008 No matter what you weigh, if you're active, you will lower your risk of disease, doctors say.

"We used to tell patients with memory concerns to do sudoku or crossword puzzles," Bachman says. "Now, we suggest exercise because it helps the brain function better."

Studies on exercise and longevity show that for every hour you exercise, you can add an hour to your life span, says Dr. Kerry Kuehl, an expert in sports medicine at Oregon Health & Science University. "But it is not just quantity of life that matters," he says. "More importantly, your quality of life improves. Exercise not only adds years to your life, but reduces aging-related disability and improves physical capacity and health status."

Kuehl runs a Human Performance Lab at OHSU that measures the body's response to exercise. Based on test results, Kuehl and his staff can recommend a diet and exercise program for your specific needs. Clients range from couch potatoes and people with physical limitations to Olympic athletes.

Some experts claim that exercise is even more important to health than diet. A Japanese study found that exercise was better than diet in reducing the effects of Alzheimer's disease.

"It's hard to separate and depends on what you are measuring," Kuehl says. A prudent diet and regular exercise are necessary for optimum health, he says, but there have been studies comparing the impact of diet and exercise alone on cardiovascular disease risk factors.

"For instance, in people with high blood pressure, the DASH diet (Dietary Approaches to Stop Hypertension) reduces blood pressure about 10 points after two weeks," he says. "In exercise training studies, the drop is 12-13 points after eight weeks of exercise, 30 minutes, three to four times per week. When exercise and diet are combined, the reduction in blood pressure is even better."

For years, we've known exercise is good for physical health, but the medical community has been more cautious about endorsing its benefits for mental health. A report from Arizona State University that examined hundreds of studies on exercise and mental health concluded that "exercise is related to positive mental health as indicated by relief in symptoms of depression and anxiety."

Want better health?No sweat

You don't have to sweat bullets to benefit from exercise. Just 150 minutes a week of moderate exercise, such as brisk walking, can do it. Divide the 150 minutes anyway you like: 30 minutes or three 10-minute walks a day, five days a week.

"The first 20 minutes of moving around, if someone has been really sedentary, provide most of the health benefits," says author Gretchen Reynolds, who writes a popular fitness blog for The New York Times. "If people want to be healthier and prolong their life span, all they really need to do is go for a walk."

But many of us get paid to sit all day. How do we stop killing ourselves? Get up at least every hour. Walk, stretch, stand, pace.

Try these tips to get moving:

1. Park far away. Develop a habit of parking farther away from your destination, at work or the mall.

2. Take the stairs. Don't be the person who takes the elevator one floor. Walk up a flight or two, then ride the rest of the way. Increase the number of flights as you get fitter.

5. Take breaks at work. Get out of your chair every hour to stretch muscles and relieve tension. Get a drink of water. Walk the perimeter of your office. Walk around the block.

6. Mow your lawn. Trim the hedge. Gardening is great exercise.

7. Play with your kids. Play ball, tag, hide-and-seek or other games. Take a family walk after dinner.

8. Walk during TV time. During commercials, walk around the house.

9. Walk while you talk. If you spend a lot of time on the phone, try pacing. Moving makes you smarter, so standing while on the phone helps.

10. Choose an active vacation. Cities are great for walking. On your next trip, skip the cruise or spa and tour the streets on foot.

Source: VersaTables.com

Dr. Jeffrey D. Rice, a Portland psychiatrist, agrees the evidence is there. When appropriate, he talks to his patients about exercise, along with discussions about sleep, diet, meditation, medication and meaningful activity, he says. "Exercise helps with mood, attention, concentration and sleep," he says. "On a biochemical level, exercise boosts levels of neurotransmitters such as serotonin and beta-endorphins. Runner's high is real."

Exercise also helps the body better modulate its response to stress, which can help patients with post-traumatic stress disorder, Rice says.

"The effects are usually immediate, and the benefits can magnify over time," he says.

"For 20 years, I tried to kill myself"

Leslie doesn't credit exercise alone for helping her back to health. In January 2011, she had bariatric surgery, which reduced her stomach from the size of a fist to a golf ball. She also cut out sugar. But getting herself to the gym also saved her life, she believes.

Six weeks after surgery, she went to the gym and rode a stationary bike at level 4, or "thumb twiddling," she says. Even that was hard.

"I had lost pounds of muscle and was covered in fat," she says. "It was also, as I think it is for so many people, an embarrassment to go to the gym and be out of breath after 20 minutes."

But those first 20 minutes "without anyone having to call an ambulance," turned into a pact she made with herself. "If I made it to the gym, went in and began using my machine of choice -- after that I could leave."

She never left.

Little by little, she pushed herself, moving from stationary bike to spin bike to elliptical to treadmill. She added weights with aerobics.

Four months after surgery, she was riding her stationary bike at an impressive level 21, the bike's hardest setting. "Hey, what's wrong with this bike?" she said to a man next to her. "I can't get it to go any higher."

"It won't go any higher," he replied.

Today, Leslie's blood sugar is normal, she says. Her blood pressure is normal, too, she lost more than 150 pounds and her feet and knees no longer hurt. She hasn't been sick in 18 months.

Her favorite exercise? Interval training, where she runs "wide open" for five minutes, then walks for two minutes, repeating for one hour.

"For 20 years, I tried to kill myself," she says. "I wrecked my heart, ruined my pancreas, lost all my muscle mass, my cholesterol was off the charts, I had knees and feet I couldn't walk on. But 20 minutes at a time of exercise, I'm no longer diabetic. I have the blood pressure of a 20-year-old. I have muscle tone."

Exercise helped her psychologically, too, she says. After a lifetime of depression, she says, exercise boosted her self-esteem, alleviated her depression and helped her do her job better. "It influenced my sense of place in the world, every aspect of my life. My relationships with my kids and with my friends have all changed. Exercise allows us a vehicle to dissipate poisons like anger, resentment, cynicism and despair.

"The point of grace in all this," Leslie says, "is, if you ever think you don't understand forgiveness, think about your body. It's willing, even in old age, to begin a transformational process despite our years of treating it with neglect and sometimes abuse."